Intraductal papilloma of the breast

by Jason Wasserman MD PhD FRCPC
August 4, 2022


What is an intraductal papilloma?

An intraductal papilloma is a non-cancerous type of breast tumour. It is called “intraductal” because it is found inside (“intra”) a small hollow structure called a duct. The purpose of a duct is to provide a path for milk to flow from the glands deep inside the breast to the nipple.

Where are intraductal papillomas normally found?

Intraductal papilloma can be found anywhere in the breast. Tumours in the central (middle) part of the breast just below the nipple tend to be larger while those that develop near the periphery (outside) of the breast are smaller.

Can someone develop more than one intraductal papilloma?

Yes, it is possible to have more than one intraductal papilloma in the same breast. Multiple papillomas are more common when the tumours are found in the periphery of the breast.

What are the symptoms of intraductal papilloma?

Intraductal papillomas that are located in the centre of the breast under the nipple may cause clear or bloody discharge from the nipple. Larger tumours may occasionally feel like a lump under the nipple. Smaller papillomas and those located in the periphery of the breast often do not cause any symptoms and may be found incidentally (by accident) when imaging of the breast is performed for another reason.

What causes an intraductal papilloma?

At present doctors do not know what causes an intraductal papilloma.

What does an intraductal papilloma look like under the microscope?

When examined under the microscope, an intraductal papilloma is made up of ductal cells that are surrounded by specialized myoepithelial cells. These two cell types connect together to form finger-like structures called papilla. The papilla should be located inside of a duct. A test called immunohistochemistry may be performed to confirm the diagnosis. This test makes it easier for pathologists to clearly see both the ductal and myoepithelial cells.

intraductal papilloma
Intraductal papilloma. This picture shows how the tumour looks under the microscope.

What other non-cancerous types of changes can be seen in an intraductal papilloma?

A variety of non-cancerous changes can be seen in an intraductal papilloma. The two most common changes are called usual ductal hyperplasia (UDH) and apocrine metaplasia. When these changes are seen they will usually be described in your pathology report.

Can precancerous conditions develop in an intraductal papilloma?

Yes, the same precancerous conditions that develop in other parts of the breast can develop in an intraductal papilloma. The two most common precancerous conditions found in this tumour are called atypical ductal hyperplasia (ADH) and ductal carcinoma in situ (DCIS). These precancerous conditions are more commonly seen in intraductal papillomas that develop in the periphery of the breast. A test called immunohistochemistry may be performed in order to support the diagnosis of ADH or DCIS. Tumours with ADH or DCIS should be removed completely because they are associated with an increased risk of developing invasive breast cancer.

Can cancer develop in an intraductal papilloma?

Yes, the same cancers that develop in other parts of the breast can develop in an intraductal papilloma. If a papilloma is removed your pathologist will carefully examine the tumour to look for any cancer.

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